You will be left with a small amount of residue with a greenish tinge. Obtain the weight of crude caffeine by difference. Add mL of hot acetone to dissolve the crude caffeine and transfer the solution to a 50 mL Erlenmeyer flask for recrystallization. Add a few drops of petroleum ether until you reach the cloud point caffeine is less soluble in this mixed solvent and is just beginning to precipitate and then cool the solution.
If you do not get a precipitate, you may have used too much acetone, carefully boil off the excess on a steam bath using a boiling stick for ebullation. A second crop of caffeine may form in the filtrate as the solvent evaporates. This second crop can also be collected by vacuum filtration but keep it separate from the first crop.
The sublimation will be performed as described by your instructor. You will use 50 mg of your caffeine to make a salicylate derivative and sublime the remainder which should be at least 50 mg. You will not take a mp of the purified caffeine which would require a sealed capillary to prevent sublimation near the melting point. Save the purified caffeine in a sealed vial. You will use some of this material for TLC analysis next week. Caffeine is a base which can react with acids to form salts.
A well characterized salt of caffeine is caffeine salicylate formed by using salicylic acid. This derivative of caffeine has an accurate melting point. Later this semester, you will be required to make solid derivatives of other compounds. The beans are once again steamed in order to eliminate any ethyl acetate that remains. Carbon dioxide supercritical fluid temperature above It behaves like gas, and permeates a porous substance, while also exhibiting liquid properties to dissolve substances.
Although supercritical carbon dioxide is non-polar, and should only be able to dissolve non-polar substances, certain co-solvents, like water, can be added so that supercritical carbon dioxide can actually dissolve polar molecules like caffeine. Water is more polar than caffeine is, so supercritical carbon dioxide, in the presence of a co-solvent like water, will dissolve the more non-polar substance, in this case, caffeine.
In order to use supercritical carbon dioxide to decaffeinate coffee beans, the beans are first steamed until they swell this is where the co-solvent, water, comes into play. After this, they are immersed in supercritical carbon dioxide which binds to the caffeine molecules and draws them out of the beans, leaving the coffee solids flavor embedded in the bean.
The carbon dioxide is then passed through a charcoal membrane that is selective toward carbon dioxide molecules. Caffeine is stopped by the membrane, because of its larger size relative to carbon dioxide, and collected. Once coffee beans have been decaffeinated, all of the extracted caffeine is made into a white powder and sold to the pharmaceutical or food industries.
The pharmaceutical industry adds caffeine into certain drugs, including many pain killers. Food industries add caffeine to certain foods like soda, because of its stimulating effect. Introduction Decaffeination is a fairly easy process since caffeine is polar and water-soluble. Swiss Water Processing The Swiss Water Processing method removes caffeine without using any chemicals, but instead applies the law of simple diffusion.
Ethyl Acetate Processing Ethyl Acetate occurs naturally in many fruits, which is why this method is often referred to as natural decaffeination. Methylene Chloride Processing Direct Method- Steamed coffee beans are rinsed directly with methylene chloride which is a polar molecule and is good solvent to organic molecules. The caffeine molecules hydrogen bond to the methylene chloride molecules, and are removed from the coffee beans, leaving the coffee solids flavor intact. During the water process method, you place the coffee beans in water and heat to around boiling point.
This removes the caffeine from the beans, but it also removes all flavor. You treat the mixture with solvent, which absorbs and evaporates the caffeine. Finally, you put the beans in the mixture again to let them absorb the flavor they lost earlier in the process. Another way to extract pure caffeine from coffee beans uses carbon dioxide. Carbon dioxide is a gas at atmospheric pressure and temperature, but if you raise the pressure and temperature, the gas changes into a supercritical liquid like a cross between a liquid and a gas.
In carbon dioxide extraction, your rinse the beans with supercritical liquid carbon dioxide. Then, you filter the supercritical liquid to get rid of the extracted caffeine, and recycle it to use it again. Claire is a writer and editor with 18 years' experience. She writes about science and health for a range of digital publications, including Reader's Digest, HealthCentral, Vice and Zocdoc.
TL;DR Too Long; Didn't Read Different methods can extract pure caffeine from coffee, including direct organic solvent extraction, the water process method and supercritical carbon dioxide extraction. How Benzene is Made.
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